Crystalline and porous covalent organic frameworks (COFs) and metal‐organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H2 evolution due to their ...long‐range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two‐dimensional (2D) COF with stable MOF. By covalently anchoring NH2‐UiO‐66 onto the surface of TpPa‐1‐COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H2 evolution under visible light irradiation. Especially, NH2‐UiO‐66/TpPa‐1‐COF (4:6) exhibits the maximum photocatalytic H2 evolution rate of 23.41 mmol g−1 h−1 (with the TOF of 402.36 h−1), which is approximately 20 times higher than that of the parent TpPa‐1‐COF and the best performance photocatalyst for H2 evolution among various MOF‐ and COF‐based photocatalysts.
Effective separation: A novel MOF/COF hybrid material assembled by covalent connecting two components, exhibits effective visible‐light‐driven photocatalytic H2 evolution due to the ideal band matching and effectively promoting the separation of the photogenerated charges and holes.
Covalent‐organic frameworks (COFs) have been recognized as a new type of promising photocatalysts for hydrogen evolution. To investigate how different functional groups attached in the backbone of ...COFs affect the overall photocatalytic H2 evolution, for the first time, we selected and synthesized a series of ketoenamine‐based COFs with the same host framework as model system. It includes TpPa−COF−X (X=−H, −(CH3)2, and −NO2) with three different groups attached in the backbone of TpPa−COF. We systematically investigated the differences in morphology, light‐absorption intensity and band gap of these 2D COFs. The results of photocatalytic H2 evolution measurements indicate that the TpPa−COF−(CH3)2 shows the best activity, while the activity of TpPa−COF−NO2 is relatively low compared to that of other two COFs in the system. Moreover, the separation ability of photogenerated charge was also followed the order of TpPa−COF−(CH3)2>TpPa−COF>TpPa−COF−NO2. The best photocatalytic H2 production performance of TpPa−COF−(CH3)2 in these systems should be mainly attributed to the better electron‐donating ability of −CH3 groups compared to −H or −NO2 group, which result in more efficient charge transferring in the inner of the material. This work demonstrates that reasonably adding electron‐donating group in TpPa−COFs can lead to a better photocatalytic H2 evolution activity, and which is meaningful for further design of efficient COF‐based photocatalysts for H2 evolution.
Photocatalysis: A series ketoenamine‐based COFs of TpPa−COF−X (X=−H, −(CH3)2, and −NO2) exhibit significant difference on the visible light absorbance and efficiency of photocatalytic H2 evolution, which can be attributed to strengthen charge carrier mobilities both in‐plane and in the stacking direction because of the electron‐donating groups.
Terahertz (THz) biological imaging has attracted intense attention due to its capability of acquiring physicochemical information in a label‐free, noninvasive, and nonionizing manner. However, ...extending THz imaging to the single‐molecule level remains a challenge, partly due to the weak THz reflectivity of biomolecules with low dielectric constants. Here, the development of graphene‐mediated THz scattering‐type scanning near‐field optical microscope for direct imaging of single proteins is reported. Importantly, it is found that a graphene substrate with high THz reflectivity and atomic flatness can provide high THz contrast against the protein molecules. In addition, a platinum probe with an optimized shaft length is found enabling the enhancement of the amplitude of the scattered THz near‐field signals. By coupling these effects, the topographical and THz scattering images of individual immunoglobulin G (IgG) and ferritin molecules with the size of a few nanometers are obtained, simultaneously. The demonstrated strategy thus opens new routes to imaging single biomolecules with THz.
Terahertz (THz) imaging has promising biomedical applications, but its application in single biomolecule detection remains challenging. Herein, by taking the advantages of high THz reflectivity and atomic smoothness of graphene and the high scattering cross‐section of long Pt probe, single IgG protein molecules are unambiguously imaged with a state‐of‐the‐art THz scattering‐type scanning near‐field optical microscope.
Bearing failure often occurs in a doubly fed induction generator. The fault diagnosis method based on the current signals has been attracted much attention. In this article, we propose different ...discrete digital models and their measure functions employing random theory. First, based on the raw current signals with the probability density function (PDF), a distributed discrete digital model is proposed; to avoid finding the PDF in the raw current signals, a discrete digital model of the moment feature and a discrete digital model of raw data are proposed. Then, six measurement functions are proposed as features of the discrete digital model for pattern recognition and condition monitoring of bearing. Finally, the effectiveness of the current method is demonstrated by comparing different signal processing methods.
•Stiffened doubly curved shell with porous microcapsule coating is investigated.•Effect of in-plane initial load is considered.•Low-velocity impact behavior in hygrothermal field is studied.
...Low-velocity impact response of stiffened metal doubly curved shallow shells with porous microcapsule coating in hygrothermal environment is analyzed considering the in-plane initial load. A modified nonlinear Hertzian contact law which ignores the influence of friction is considered for the low velocity impact problem. Based on the classical shell theory considering the von Kármán geometric nonlinearity, the governing equations of motion for this structure are derived from the Hamilton’s variation principle while the finite difference method (FDM) and Newmark-β algorithm are used to solve the equations. The effects of temperature and moisture, initial velocity of impactor, properties of metal substrate, initial load, geometry parameters of microcapsules, geometry parameters of the stiffened shell and porosity on the transient impact response of the stiffened shell are examined and analyzed. Initial impact velocity, properties of metal substrate and porosity have a significant effect on contact force and central deflection. Normal stress is greatly affected by temperature, properties of metal substrate, geometry parameters of the stiffened shell and porosity. Moreover, the impact resistance of stiffened shells is enhanced by the in-plane initial tensile load while the effect of in-plane initial compressive load is opposite.
Diabetic kidney disease (DKD) is among the most important causes for chronic kidney disease. Anthocyanins (ANT) are polyphenolic compounds present in various food and play an important role in ...ameliorating hyperglycemia and insulin sensitivity. However, the effects of ANT in DKD are still poorly understood. This study aimed to investigate the effect of ANT (cyanidin-3-O-glucoside C3G) on the renal function of DKD, and whether the anti-DKD effect of ANT is related to metabolic pathways.
To explore the role of ANT in DKD, we performed the examination of blood glucose, renal function, and histopathology. As for the mechanism, we designed the label-free quantification proteomics and nontargeted metabolomics analysis for kidney and serum. Subsequently, we revealed the anti-DKD effect of ANT through the bioinformatic analysis.
We showed that the fasting blood glucose level (- 6.1 mmol/L, P = 0.037), perimeter of glomerular lesions (- 24.1 μm, P = 0.030), fibrosis score of glomerular (- 8.8%, P = 0.002), and kidney function (Cystatin C: - 701.4 pg/mL, P = 0.043; urine creatinine: - 701.4 mmol/L, P = 0.032) were significantly alleviated in DKD mice after ANT treatment compared to untreated in the 20th week. Further, proteins and metabolites in the kidneys of DKD mice were observed to be dramatically altered due to changes in amino acid metabolism with ANT treatment; mainly, taurine and hypotaurine metabolism pathway was upregulated (P = 0.0001, t value = 5.97). Furthermore, upregulated tryptophan metabolism (P < 0.0001, t value = 5.94) and tyrosine metabolism (P = 0.0037, t value = 2.91) pathways had effects on serum of DKD mice as responsed ANT regulating.
Our results suggested that prevention of the progression of DKD by ANT could be related to the regulation of amino acid metabolism. The use of dietary ANT may be one of the dietary strategies to prevent and treat DKD.
•Hygrothermal coupling conduction model is established.•Geometric nonlinear of shell is investigated in hygrothermal effect.•Navier solution with hygrothermal effect is proposed.
During the service ...life of polymer matrix composites, various loading conditions often occur. To use such materials effectively in high-performance applications, their behaviors under hygrothermal effects should be clearly understood. Firstly, a laminated spherical shell panel is established under hygrothermal effects, followed by geometric properties’ analysis and internal forces analysis of the shell. Then, the constitutive relations related to the hygrothermal effects are considered in the laminated spherical shell panel, and equations of motion with geometric nonlinearity are derived by employing Hamilton’s principle; thereafter, solution of equations of motion is obtained using the Navier solution technique. Finally, influences of the hygrothermal effects on nondimensionalized center deflections, nondimensionalized fundamental natural frequency, and vibration-deflection amplitude for the shell are discussed.
DNA oligonucleotides with a 5-base mutation at the 3'-terminus were investigated by terahertz (THz) spectroscopy in a marker-free manner. The four single-stranded oligonucleotides with 17nt have been ...detected with specificity on a microfluidic chip, and corroborated by spectral measurements with split-ring resonators. The number of hydrogen bonds formed between the oligonucleotide and its surrounding water molecules, deemed a key contribution to the THz absorption of biological solutions, was explored by molecular dynamics simulations to explain the experimental findings. Our work underlies the feasibility of THz spectroscopy combined with microstructures for marker-free detection of DNA, which may form the basis of a prospective diagnostic tool for studying genic mutation.
Background and Purpose
Limonin, a naturally occurring tetracyclic triterpenoid, has extensive pharmacological effects. Its role in cardiac hypertrophy remains to be elucidated. We investigated its ...effects on cardiac hypertrophy along with the potential mechanisms involved.
Experimental Approach
The effects of limonin on cardiac hypertrophy in C57/BL6 mice caused by aortic banding, plus neonatal rat cardiac myocytes (NRCMs) stimulated with phenylephrine to induce cardiomyocyte hypertrophy in vitro were investigated.
Key Results
Limonin markedly improved the cardiac function and heart weight in aortic banded mice. Limonin‐treated mice and NRCMs also produced fewer cardiac hypertrophy markers than those treated with the vehicle in the hypertrophic groups. Sustained aortic banding‐ or phenylephrine‐stimulation impaired cardiac sirtuin 6 (SIRT6) protein levels, which were partially reversed by limonin associated with enhanced activity of PPARα. Sirt6 siRNA inhibited the anti‐hypertrophic effects of limonin in vitro. Interestingly, limonin did not influence Sirt6 mRNA levels, but regulated ubiquitin levels. Thus, the protein biosynthesis inhibitor, cycloheximide and proteasome inhibitor, MG‐132, were used to determine SIRT6 protein expression levels. Under phenylephrine stimulation, limonin increased SIRT6 protein levels in the presence of cycloheximide, but it did not influence SIRT6 expression in the presence of MG‐132, suggesting that limonin promotes SIRT6 levels by inhibiting its ubiquitination degradation. Furthermore, limonin inhibited the degradation of SIRT6 by activating ubiquitin‐specific peptidase 10 (USP10), while Usp10 siRNA prevented the beneficial effects of limonin.
Conclusion and Implications
Limonin mediates the ubiquitination and degradation of SIRT6 by activating USP10, providing an attractive therapeutic target for cardiac hypertrophy.
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•Decoupling of the bearing composite failure mechanism has been avoided.•The amount of statistical information rich in the raw signal has been utilized.•The sampling uncertainty caused by the average ...multi-segment signal and the fluctuation of the signal with time have been solved.•Subjective cognitive uncertainty and objective experimental uncertainty of experimental data have been considered.
Feature extraction leads to the loss of statistical information of raw data and ignores the sampling uncertainty and the fluctuations in the signal over time in mechanical fault diagnosis. In this paper, novel modeling methods for mechanical signals based on probability box theory were proposed to solve the above problem. First, the type of random distribution of the bearing signals were analyzed. Then, a Dempster-Shafer structure was obtained to establish a probability box model. To address the identification difficulty of the type of random distribution for the bearing signals, a second probability box model was established based on a vector consisting of features from the bearing signals. If the data are not found to follow a random distribution, a third modeling method based on the definition of probability boxes was proposed. The effectiveness and applicability of the three proposed models were compared with experimental data from rolling element bearings. The combination of probability box theory and mechanical fault diagnosis theory can open up a new research direction for mechanical fault diagnosis.
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